Inorganic fibrous regularly shaped article and method for adjusting hardness thereof

ABSTRACT

An inorganic fibrous shaped product including organic fiber that includes at least biosoluble inorganic fiber having the following composition and an organic thickener, and including no colloidal silica: [Composition] SiO 2 : 70 to 82 wt %; CaO: 10 to 29 wt %; MgO: 1 wt % or less; Al 2 O 3 : less than 5 wt %; and the total of SiO 2 , CaO, MgO and Al 2 O 3  exceeds 98 wt %.

TECHNICAL FIELD

The invention relates to an inorganic fibrous shaped product that can beused as a sealing agent or a packing agent and a method for adjustingthe hardness thereof.

BACKGROUND ART

Inorganic fiber is light in weight, easy to handle, and has excellentheat resistance. Therefore, inorganic fiber is used as a heat-insulatingsealing material, for example. On the other hand, in recent years, aproblem has been pointed out that inorganic fiber is inhaled by a humanbody and the inhaled fiber invades the lung. Therefore, biosolubleinorganic fiber that does not cause or hardly cause problems even ifinhaled by a human body has been developed (Patent Documents 1 and 2,for example).

According to applications, biosoluble inorganic fiber is not only usedas the raw material of textiles such as a rope, a yarn and a cloth, butalso secondarily processed to and used as a shaped product such as ablanket, a board and a felt or an unshaped product such as a coatingmaterial and mortar.

When a shaped product is used as a joint filler in a heat-treatmentapparatus, an industrial furnace or an incinerator, a joint filler thatfills a gap of refractory tiles, heat-insulating bricks, shells andrefractory mortars, a sealing material, and a packing material,flexibility and cushion properties are required such that constructionof joints can be conducted without forming gaps. When construction iscarried out on a curved surface or the like, since a shaped product isapplied after processing variously, in addition to flexibility, hardnessis required for the need of attaining working accuracy or dimensionalaccuracy. As mentioned above, flexibility and hardness are requiredaccording to applications. Further, in order not to be deformed duringuse at high temperatures, it is preferred that a shaped product have asmall heat shrinkage.

A conventional shaped product such as a board contains an inorganicbinder (colloidal silica) in order to allow it to be hard. However, ifcolloidal silica is contained, when a shaped product is used at hightemperatures, a problem arises that strength is lowered or cushionproperties are deteriorated due to advancement in crystallization.Further, there is a problem that, due to deterioration in flexibility, ashaped product cannot retain its shape after construction, and as aresult, it drops from the location of construction or a gap is formedbetween the location of construction and the shaped product.

RELATED ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-A-2001-270737-   Patent Document 2: JP-T-2005-514318

SUMMARY OF THE INVENTION

An object of the invention is to provide an inorganic fibrous shapedproduct that does not contain colloidal silica and has various degreesof flexibility and hardness, and heat resistance, and a method foradjusting the hardness thereof.

According to the invention, the following method for adjusting thehardness of an inorganic fibrous shaped product can be provided.

-   1. An inorganic fibrous shaped product comprising organic fiber that    comprises biosoluble inorganic fiber having at least the following    composition and an organic thickener, and comprising no colloidal    silica:

[Composition]

SiO₂: 70 to 82 wt %;

CaO: 10 to 29 wt %;

MgO: 1 wt % or less;

Al₂O₃: less than 5 wt %; and

the total of SiO₂, CaO, MgO and Al₂O₃ exceeds 98 wt %.

-   2. The inorganic fibrous shaped product according to 1, further    comprising a fixing agent.-   3. The inorganic fibrous shaped product according to 2, wherein the    fixing agent is one or more selected from sulfates, nitrates,    acetates and hydrochlorides of each of aluminum, magnesium, calcium,    sodium and potassium.-   4. A method for adjusting the hardness of the surface of the    inorganic fibrous shaped product according to any of 1 to 3, wherein    the amount of at least one of an organic thickener and a fixing    agent is changed.

According to the invention, it is possible to provide an inorganicfibrous shaped product that does not contain colloidal silica and hasvarious degrees of flexibility and hardness, and heat resistance, and toprovide a method for adjusting the hardness thereof.

MODE FOR CARRYING OUT THE INVENTION

The inorganic fibrous shaped product of the invention at least comprisesprescribed inorganic fiber (hereinafter may often referred to as the“specific inorganic fiber”) and an organic thickener. The inorganicfibrous shaped product of the invention does not contain colloidalsilica. Further, the inorganic fibrous shaped product of the inventiondoes not have to contain a metal alkoxide, a glass raw materialcomposition (borosilicate glass, frit 3249 (manufactured by FerroCorporation: 3.5% CaO; 12.2% MgO; 28.9% B₂O₃; 13.3% Al₂O₃; and 42.1%SiO₂) or the like), a sol (alumina borate sol or the like), and aninorganic binder such as an acid alumina phosphate does not have to becontained. Further, a thermosetting resin such as a phenol resin and anepoxy resin does not have to be contained.

Organic thickeners include a natural thickener and its derivative or avinyl-based, vinylidene-based, polyester-based, polyamide-based,polyether-based, polyglycol-based, polyvinyl alcohol-based, polyalkyleneoxide-based and polyacrylic acid-based thickeners. Specific examplesthereof include cellulose-based thickeners such as CMC (carboxymethylcellulose), MC (methyl cellulose), albumin, casein, alginic acid, agar,starch, polysaccharide, PVA (polyvinyl alcohol), PVB (polyvinylbutyral), acrylic emulsion or the like. These may be used alone or incombination of two or more. A polyacrylic acid-based thickener, acellulose-based thickener and starch are preferable. The shaped productof the invention may contain an organic thickener in a substantiallyun-molten state.

The inorganic fibrous shaped product of the invention may furthercontain a fixing agent in order to allow an organic thickener to befixed to fibers. As examples of the fixing agent, sulfates, nitrates,acetates and hydrochlorides of each of aluminum, magnesium, calcium,sodium and potassium can be given.

In order to allow flocs to be formed in a slurry, a flocculant may becontained. A general-purpose flocculant may be used, and the type andamount may appropriately be selected according to the state of theresulting flocs. Flocculants are not necessarily be contained.

The specific inorganic fiber used in the invention has the followingcomposition. The fiber having the following composition has excellentbiosolubility and fire resistance after heating.

SiO₂: 66 to 82 wt %

CaO: 10 to 34 wt %

MgO: 3 wt % or less

Al₂O₃: 5 wt % or less

The total of SiO₂, CaO, MgO and Al₂O₃ exceeds 98 wt %.

The following composition can preferably be exemplified.

SiO₂: 66 to 82 wt % (it can be 68 to 80 wt %, 70 to 80 wt %, 71 to 80 wt% or 71 to 76 wt %, for example)

CaO: 10 to 34 wt % (it can be 20 to 30 wt % or 21 to 26 wt %, forexample) MgO: 3 wt % or less (it can be 1 wt % or less, for example)

Al₂O₃: 5 wt % or less (it can be 3.5 wt % or less or 3 wt % or less, orit can be 1 wt % or more or 2 wt % or more, for example)

Other oxides: less than 2 wt %

If SiO₂ is contained in the above-mentioned amount range, the inorganicfiber has excellent heat resistance. If CaO and MgO are contained in theabove-mentioned amount range, the inorganic fiber has excellentbiosolubility before and after heating.

The Al₂O₃ content can be 3.4 wt % or less or 3.0 wt % or less, forexample, or it can be 1.1 wt % or more and 2.0 wt % or more. The Al₂O₃content is preferably 0 to 3 wt %, more preferably 1 to 3 wt %. If Al₂O₃is contained in this amount range, a higher strength can be achieved.

The above-mentioned inorganic fiber may contain, as other oxides, one ormore selected from alkali metal oxides (K₂O, Na₂O or the like), Fe₂O₃,ZrO₂, P₂O₅, B₂O₃, TiO₂, MnO, R₂O₃ (R is selected from Sc, La, Ce, Pr,Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y or a mixture thereof) orthe like. They need not be contained. The content of each of otheroxides may be less than 1.0 wt %, 0.2 wt % or less or 0.1 wt % or less.As for the alkali metal oxide, the content of each oxide may be lessthan 1.0 wt % or 0.2 wt % or less, and the total of alkali metal oxidesmay be less than 1.0 wt % or 0.2 wt % or less.

The total content of SiO₂, CaO, MgO and Al₂O₃ may exceed 99 wt %.

The fiber having the above-mentioned composition is biosoluble. Ingeneral, biosoluble fiber is fiber having a physiological salinedissolution ratio at 40° C. of 1% or more.

The physiological saline dissolution ratio is measured by the followingmethod, for example. Specifically, first, 1 g of the sample obtained bypulverizing inorganic fibers to 200 meshes or less and 150 mL ofphysiological saline are put in a conical flask (volume: 300 mL). Thisflask is placed in an incubator of 40° C., and a horizontal vibration(120 rpm) is continuously applied for 50 hours. Thereafter, theconcentration (mg/L) of each element contained in a filtrate obtained byfiltration is measured by an ICP emission spectrometry apparatus. Basedon the measured concentration of each element and the content (wt %) ofeach element in inorganic fiber before dissolution, the physiologicalsaline dissolution ratio (%) is calculated. That is, if the measurementelements are silicon (Si), magnesium (Mg), calcium (Ca) and aluminum(Al), the physiological saline dissolution ratio C(%) is calculated inaccordance with the following formula: C(%)=[Amount of filtrate(L)×(a1+a2+a3+a4)×100]/[Weight (mg) of inorganic fiber beforedissolution×(b1+b2+b3+b4)/100]. In this formula, a1, a2, a3 and a4 arerespectively the measured concentration (mg/L) of silicon, magnesium,calcium and aluminum and b1, b2, b3 and b4 are respectively the content(wt %) of silicon, magnesium, calcium and aluminum in the inorganicfiber before dissolution.

As the method for producing the above-mentioned inorganic fiber, knownmethods such as the blowing method and the spinning method can bementioned.

The inorganic fibrous shaped product may contain other inorganic fiberin addition to the above-mentioned specific inorganic fiber. Among 100parts by weight of the inorganic fiber, the content of the specificinorganic fiber may be 50 wt % or more, 60 wt % or more, 80 wt % or moreor 100 wt %.

Refractory fiber composed mainly of silica and alumina (silica: 4 to 60wt %, alumina: 40 to 96 wt %), rock wool (for example, the SiO₂ contentis 30 to 50 mass %, the Al₂O₃ content is 10 to 20 mass %, the MgOcontent is 1 to 10 mass %, the CaO content is 20 to 40 mass %, the Fe₂O₃content is 0 to 3 mass % and the MnO content is 0 to 1 mass %), carbonfiber, slag wool, glass wool, silica fiber, silicon carbide fiber, boronnitride fiber, zirconia fiber, calcium silicate fiber, and other naturalmineral fiber can be given.

The inorganic fibrous shaped product may contain inorganic powder,anti-foaming agents, pH-adjusting agents or the like.

The content of an organic thickener is normally 0.01 to 60 parts byweight, preferably 0.1 to 30 parts by weight, more preferably 0.5 to 20parts by weight, and further preferably 1 to 15 parts by weight, whenthe total content of all of the inorganic fiber contained in the shapedproduct is taken as 100 parts by weight. If the content of an organicthickener is 60 parts by weight or more, dehydration forming becomesdifficult. If the shaped product is used at high temperatures, organiccomponents may cause a gas to be generated. Therefore, the content of anorganic thickener may be appropriately adjusted such that the inorganicfibrous shaped product can exhibit its function or can satisfy requiredproperties according to applications.

A fixing agent may normally be contained in an amount of 0 to 10,preferably 0.5 to 10, and more preferably 1 to 7, if the content of anorganic thickener is taken as 1. In the shaped product of the invention,a fixing agent is normally contained in an amount of 0 to 20 parts byweight, preferably 0.01 to 15 parts by weight, more preferably 0.5 to 10parts by weight and further preferably 1 to 10 parts by weight, if thetotal content of the inorganic fiber is taken as 100 parts by weight.The total of an organic thickener and a fixing agent is preferably 0.1to 30 wt %, preferably 1 to 20 wt %, preferably 1 to 15 wt % andpreferably 1 to 10 wt %.

The organic fibrous shaped product may be configured such that the totalcontent of the inorganic fiber and the organic thickener (if organicpowder and/or a fixing agent are contained, the total content of theinorganic fiber, the organic thickener, the inorganic powder and thefixing agent) becomes 90 wt % or more, 95 wt % or more, 98 wt % or more,99 wt % or more or 100 wt %.

The inorganic fibrous shaped product is preferably in the shape of afabric such as a felt or in the shape of a flexible sheet. The shapedproduct such as a felt can be used as a single body without the need ofscattering, applying or stacking other materials on the surface thereof.The shaped product having flexibility or cushion properties can changeits form easily, and therefore, can be pushed into a gap between jointseasily, for example. The thickness is not particularly restricted, butis normally 5 mm or more, preferably 10 to 50 mm.

The hardness and flexural strength of the inorganic fibrous shapedproduct of the invention can be appropriately adjusted according toapplications by changing the amount of an organic thickener and/or afixing agent. With an increase in the amount of an organic thickener anda fixing agent, the organic fibrous shaped product has higher hardness.

The surface hardness of the inorganic fibrous shaped product in thenormal state (unheated) varies depending on the application, but isnormally 1 to 60°. The method for measuring the surface hardness isdescribed in the Examples.

Further, a flexural strength in the normal state of 0.03 to 0.6 Mpa ispreferable since the handling properties and the working accuracy of theinorganic fibrous shaped product are improved. The method for measuringthe flexural strength is described in the Examples.

The heat shrinkage of the inorganic fibrous shaped product after heatingat 1100° C. for 24 hours is preferably 2% or less, more preferably 1% orless. The heat shrinkage can be further lowered by using theabove-mentioned specific inorganic fiber having a low heat shrinkage andby appropriately combining an organic thickener and a fixing agent. Themethod for measuring the heat shrinkage is described in the Examples.

The shaped product can be produced by a known method such as dehydrationforming or the like. For example, it can be produced by a method inwhich a raw material containing the inorganic fiber and an organicthickener and a dispersion medium are mixed to form a slurry, the slurryis flown in a die to conduct forming, and the formed product is dried.Drying is preferably conducted at a temperature that is not higher thanthe melting temperature. The shaped product of the invention can beproduced by using a used shaped product. However, since it is difficultto control the amount of an organic substance, normally, a used shapedproduct is not used. If the amount of an organic substance is large, alarge amount of gas is generated when heating.

When dehydration forming is conducted, a slurry is produced by mixingcomponents with a solvent. The amount of a solvent is normally 1000 to100000 parts by weight, preferably 1500 to 80000 parts by weight, andfurther preferably 2000 to 60000 parts by weight, when the total amountof all inorganic fiber contained in the shaped product is taken as 100parts by weight.

Normally, water is used as the solvent. A polar organic solvent may beused, or may be added partially, but water is preferable as the solvent.As for water, one that is normally used on the industrial basis may beused, and examples of usable water include distilled water, ion exchangewater, tap water, groundwater and industrial water.

EXAMPLES Examples 1 to 16 (1) Production of Felt

Inorganic fiber A comprising 73 mass % of SiO₂, 24 mass % of CaO, 0.3mass % of MgO and 2 mass % of Al₂O₃ and an organic thickener selectedfrom CMC (organic thickener), starch (organic thickener) and an acrylicemulsion (organic thickener) were mixed with water in amounts shown inTables 1 to 3, whereby a raw material slurry was prepared. As for CMC orstarch, the concentration of solid matters had been adjusted to 0.5 to5% in advance, and CMC or starch was added in the state where it wasfully dissolved or swollen in water.

In Tables 1 to 3, as for the amount of components other than theinorganic fiber, the amount is indicated in terms of part by weight whenthe amount of the inorganic fiber A is taken as 100 parts by weight.Water was used in an amount of 3000 parts by weight when the amount ofthe inorganic fiber A is taken as 100 parts by weight.

This raw material slurry was flown in a forming die in which a net wasprovided in the bottom part thereof. The water contained in the rawmaterial slurry was sucked and removed through the net of the formingdie. Thereafter, the dehydrated raw material was dried by heating in adrier, whereby felts each having a thickness of 25 mm were obtained.

(2) Evaluation of Felt

The following evaluation was conducted for the resulting felts. Theresults are shown in Tables 1 to 3.

(i) Heat Shrinkage

A sample (length: 150 mm, width: 50 mm) taken out from the felt wasfired at 1100° C. for 24 hours. Before and after the firing, the lengthin the longitudinal direction was measured, and the heat shrinkage wasobtained according to the following formula:

[(Measured value before heating−Measured value after heating)/Measuredvalue before heating]×100

(ii) Flexural Strength

For a sample (length: 150 mm, width: 50 mm) taken out from the felt, thebreaking load thereof was measured by using a three-point bendingtesting machine (Tensilon). The flexural strength was calculatedaccording to the following formula:

Bending strength (MPa)={3×maximum load (N)×distance (mm) between thecenters of support rolls}/{2×width (mm) of insulatingmaterial×(thickness (mm) of insulating material)²}

(iii) Hardness

The pressure surface of an Asker Durometer Type C was brought in contactwith the surface of the felt that was held horizontally such that theindenter point of the durometer became vertical to the felt surface. Thescale of the durometer was immediately read. An average value ofmeasurement values at 5 locations was taken as the hardness)(°) of thetest piece.

TABLE 1 Example 1 Example 2 Example 3 Example 4 Example 5 Example 6Inorganic fiber Inorganic fiber A 100 100 100 100 100 100 Organicthickener CMC 1 3 5 7 10 15 Starch Acrylic emulsion Fixing agentAluminum sulfate Heat shrinkage 1100° C. × 24 hr 0.20 0.00 0.60 0.40 0.50.4 Flexural strength Unheated 0.03 0.02 0.04 0.07 0.1 0.2 HardnessSurface 3 15 23 25 35 50

TABLE 2 Example Example Example 7 Example 8 Example 9 10 11 Inorganicfiber Inorganic fiber A 100 100 100 100 100 Organic thickener CMC 5 5 55 5 Starch 1 3 5 7 10 Acrylic emulsion Fixing agent Aluminum sulfateHeat shrinkage 1100° C. × 24 hr 1.6 1.2 1.2 1.4 1.5 Flexural strengthUnheated 0.04 0.05 0.03 0.05 0.06 Hardness Surface 5 6 11 13 15

TABLE 3 Example Example Example Example Example 12 13 14 15 16 Inorganicfiber Inorganic fiber A 100 100 100 100 100 Organic thickener CMC 5 5 55 5 Starch Acrylic emulsion 1 3 5 7 10 Fixing agent Aluminum sulfateHeat shrinkage 1100° C. × 24 hr 1.2 1.2 1.2 1.2 0.6 Flexural strengthUnheated 0.05 0.13 0.17 0.2 0.24 Hardness Surface 8 12 28 32 40

Comparative Examples 1 to 3

The components shown in Table 4 were mixed in amounts shown in Table 4.The mixture was subjected to dehydration forming to produce formedbodies (board) each having a thickness of 25 mm. Evaluation wasconducted in the same manner as in Example 1. The results are shown inTable 4.

The inorganic fiber B comprises 53 mass % of SiO₂ and 47 mass % ofAl₂O₃.

TABLE 4 Com. Ex. Com. Ex. Com. Ex. 1 2 3 Inorganic fiber Inorganic fiberA 100 100 Inorganic fiber B 100 Organic thickener CMC Starch 3 4.5 4.5Inorganic binder Colloidal silica 10 5 5 Fixing agent Aluminum sulfateFlocculant 2 0.5 0.5 Heat shrinkage 1100° C. × 24 hr 1.00 3 2.1 Flexuralstrength Unheated 0.80 0.5 0.5 Hardness Surface 55 50 50

Examples 17 to 36

The components shown in Tables 5 and 6 were mixed in amounts shown inTables 5 and 6. Felts each having a thickness of 25 mm were produced andevaluated in the same manner as in Example 1. The results are shown inTables 5 and 6.

TABLE 5 Example Example Example Example Example Example Example Example17 18 19 20 21 22 23 24 Inorganic fiber Inorganic fiber A 100 100 100100 100 100 100 100 Organic thickener CMC 5 5 5 5 5 5 5 5 Starch Acrylicemulsion Fixing agent Aluminum sulfate 0 0.25 0.5 1 2 3 4 5 Heatshrinkage 1100° C. × 24 hr 1.02 1.05 0.79 0.82 0.59 0.61 0.68 0.77Flexural strength Unheated 0.03 0.06 0.07 0.07 0.21 0.25 0.38 0.4Hardness Surface 4 6 8 9 35 32 33 45 Example Example Example ExampleExample Example Example Example 25 26 27 28 29 30 31 32 Inorganic fiberInorganic fiber A 100 100 100 100 100 100 100 100 Organic thickener CMC3 3 3 3 1 1 1 1 Starch Acrylic emulsion Fixing agent Aluminum sulfate1.8 4 6 7 0.5 1 2 3 Heat shrinkage 1100° C. × 24 hr 0.58 1.13 0.60 0.62−0.27 0.25 0.73 0.67 Flexural strength Unheated 0.19 0.33 0.47 0.50 0.020.03 0.04 0.04 Hardness Surface 23 35 40 48 2 1 4 5

TABLE 6 Example Example Example Example Composition 33 34 35 36Inorganic fiber Inorganic fiber A 100 100 100 100 Organic thickener CMC5 5 5 3 Starch Acrylic emulsion Fixing agent Aluminum nitrate 1 2 3 2Heat shrinkage 1100° C. × 24 hr 0.76 0.78 0.73 0.89 Flexural strengthUnheated 0.12 0.31 0.49 0.14 Hardness Surface 19 38 45 21

From Tables 1 to 6, it can be understood that the felts of the Examplescan have appropriate values of heat shrinkage, flexural strength andhardness without using an inorganic binder. The heat shrinkage of thefelts is equivalent to or smaller than that of the boards, and theflexural strength (flexibility) of the felts is equivalent to or smallerthan that of the boards. Further, it can be understood that the hardnessof the felt can be increased to a level that is equal to that of theboard by increasing the amount of an organic thickener or the amount ofa fixing agent and an organic thickener.

INDUSTRIAL APPLICABILITY

The inorganic fibrous shaped product of the invention can be used invarious applications as a joint filler in a heat treatment apparatus, anindustrial kiln or an incinerator; a joint filler that fills a gap ofrefractory tiles, heat-insulting bricks, shells and refractory mortars,a sealing material, a packing material, a heat insulating material or analternative to asbestos.

Although only some exemplary embodiments and/or examples of thisinvention have been described in detail above, those skilled in the artwill readily appreciate that many modifications are possible 2 0 in theexemplary embodiments and/or examples without materially departing fromthe novel teachings and advantages of this invention. Accordingly, allsuch modifications are intended to be included within the scope of thisinvention.

The documents described in this specification and the Japaneseapplication specification claiming priority under the Paris Conventionare incorporated herein by reference in its entirety.

1. An inorganic fibrous shaped product comprising organic fiber thatcomprises at least biosoluble inorganic fiber having the followingcomposition and an organic thickener, comprising no colloidal silica:[Composition] SiO₂: 70 to 82 wt %; CaO: 10 to 29 wt %; MgO: 1 wt % orless; Al₂O₃: less than 5 wt %; and the total SiO₂, CaO, MgO and Al₂O₃exceeds 98 wt %.
 2. The inorganic fibrous shaped product according toclaim 1, further comprising a fixing agent.
 3. The inorganic fibrousshaped product according to claim 2, wherein the fixing agent is one ormore selected from sulfates, nitrates, acetates and hydrochlorides ofeach of aluminum, magnesium, calcium, sodium and potassium.
 4. A methodfor adjusting the hardness of the surface of the inorganic fibrousshaped product according to claim 1 wherein the amount of at least oneof an organic thickener and a fixing agent is changed.